Pumps are critical components in wastewater treatment facilities. The Sanford (Maine) Sewerage District experienced just how critical when the pumps feeding biosolids to the centrifuges at its wastewater treatment plant began to fail.The district, serving a community of 21,000, has been in operation since 1947. The treatment plant (4.4 mgd design, 1.56 mgd average) is fed by 70 miles of gravity sewers and 16 pumping stations. It also treats the septage from surrounding towns.The activated sludge oxidation ditch treatment process includes biological nutrient removal with chemical addition for additional removal of phosphorus. This is followed by multimedia filtration (Roberts Filter
